1. Field of the Invention.
The present invention relates to compositions of matter which are useful for water softening.
2. Description of the Art.
Aluminosilicates which have high calcium and magnesium exchange rates and capacity have been added to water softening and detergent products to remove water hardness. Effective removal of calcium and magnesium ions from water when considered in the context of detergent products is important in that those ions can precipitate anionic surfactants rendering the former less effective in fabric cleaning. Moreover if the calcium and magnesium ions are not removed from water used for washing, these ions will interact with soils on the fabrics thus interferring with soil removal.
Water softening and detergent products utilizing the aluminosilicates which form a part of the present invention, are described in several references. For instance, Corkill et al in U.S. Patent Application Ser. No. 450,266, filed Mar. 11, 1974, describes the use of such aluminosilicates which are added to detergent compositions by admixing the aluminosilicate with the remaining components, or by spray drying the aluminosilicate with the remaining components of the composition.
U.S. Ser. No. 479,951, filed June 17, 1974, Krummel et al, describes the formulation of a detergent composition containing aluminosilicates and alkali metal silicates. In Krummel et al the silicates are present at a very low level to avoid the interaction with the aluminosilicate. This product is formed by spray drying all of the components in the composition including the aluminosilicate and the alkali metal silicate.
In the application of Ohren et al, U.S. Ser. No. 598,292, filed July 23, 1975, a detergent composition is described which is prepared by spray drying the aluminosilicates of the present invention, high levels of alkali metal silicates, and alkali metal ortho or pyrophosphates. The problem of interaction of the aluminosilicate and the alkali metal silicate is minimized by carefully controlling the moisture content of the product during the spray drying operation. This moisture control has the additional benefit of allowing the alkali metal orthophosphate or pyrophosphate to function as a precipitating builder.
A further description of aluminosilicates which have utility in the present invention for water softening is found in U.S. Patent Application Ser. No. 379,881, filed July 16, 1973 in the name of Madison et al. Further descriptions of aluminosilicate materials having utility for water softening in detergent compositions are found in Belgian Patents Nos. 813,581 and 828,753, South African Patent Application No. 74/2862, South African Patent Application No. 74/3319, and Netherlands Patent Application No. 74/03383.
Materials which are suitable as organic agglomerating compounds have been described in United States Patent Application Ser. No. 631,026, filed Nov. 11, 1975 by Ashcraft and in U.S. Pat. No. 2,806,001, issued on Sept. 10, 1957.
It has been found that the incorporation of the aluminosilicate materials into detergent and water softening compositions described above presents great difficulties. For instance, if aluminosilicates are to be admixed into the composition as a dry material, a considerable quantity of dust can be generated by improper handling of the finely divided aluminosilicate. Moreover, the aluminosilicates per se are not free-flowing. It is also noted that if the aluminosilicate materials with which the present invention is concerned are admixed dry with the remainder of a composition, that segregation of the fine aluminosilicate materials will occur during packing and transportation of the finished product. The segregation is extremely undesirable in that when the consumer uses the product the lack of uniformity may result in over-usage or underusage. Moreover, consumers are accustomed to using detergent products of uniform quality and appearance such as the phosphate built products currently marketed. Thus it is desirable that aluminosilicate products designed for laundry or water softening purposes should be as compatible as possible in both appearance and performance with currently marketed phosphate products. While the present invention may contain phosphate salts at a low level the reduction of these materials is desirable because of the suspected ability of the phosphates to eutrophy lakes and rivers.
The proposed alternatives to admixing the fine aluminosilicate materials into water softening and detergent compositions includes premixing the aluminosilicate with the remaining detergent components such as alkali metal silicates, and other detergent components and then spray drying the slurry to form uniformly sized granules containing essentially all of the components in the composition.
Compositions in which the aluminosilicates have been prepared by spray drying a slurry containing surfactants and alkali metal silicates have proved to be extremely difficult to manufacture with requisite uniformity. For instance, it has been observed that when the aluminosilicates are exposed to alkali metal silicates in an aqueous slurry that a chemical reaction takes place, leading to cross-polymerization of the aluminosilicate molecules through bridging by the alkali metal silicate. While elimination of the alkali metal silicate from the detergent composition would seem to be a desirable solution it is not practical. The alkali metal silicates are highly favored components in detergent compositions because of their ability to protect washing machine surfaces from corrosion and also aid in forming crisp, free-flowing granules.
Another possible alternative which could be utilized to prevent the interaction of the aluminosilicate and the alkali metal silicate would be to admix the alkali metal silicate into the final composition. Aiside from the fact that the alkali metal silicate is needed in the granule containing the organic detergent components to provide desirable granule characteristics, there is no practical manner for admixing alkali metal silicates into the final composition. This decision is predicated upon the fact that the alkali metal silicates when purchased in a dry form are highly voluminous, thus requiring large storage facilities and plant capability for admixing large quantities of the silicate. It is also noted that dry alkali metal silicates as well as being of very low density, are relatively expensive when compared to the price of alkali metal silicate solutions which are commercially available.
In the copending application of Ohren, Serial Number 655,801 filed Feb. 6, 1976, herein incorporated by reference, similar particulate compositions are disclosed. These compositions while performing eminently well for water softening have a tendency to be friable.
Friability, defined as the inability of a composition to maintain its integrity without crumbling is an undesirable property. The friability of the aforementioned particulate can be overcome to a certain extent by increasing the amount of the agglomerating compound utilized in relation to the aluminosilicate. This remedy is, however, undesirable in that it is not a complete cure of the friability of the particulate and the agglomerating compound is relatively expensive. Thus it remains to prepare a particulate in accordance with the objectives of the Ohren application in mind with substantially reduced friability.
It is therefore an object of the present invention to prepare a free-flowing, water softening or detergent composition containing an aluminosilicate, an inorganic salt, and an organic agglomerating compound in particulate form.
It is a further object of the present invention to prepare an aluminosilicate-containing product for water softening or detergent compositions which provides a substantially non-friable product.
It is a further object of the present invention to prepare an aluminosilicate-containing composition in which the aluminosilicate does not segregate from the remaining components during transportation and storage.
It has been found that the organic agglomerating compound, the inorganic salt, and the aluminosilicates when prepared according to the invention, form free-flowing consumer acceptable particulate compositions which are substantially non-friable. Surprisingly, very low levels of the inorganic salts substantially reduce friability.
It has also been found that the particulate when admixed into detergent compositions cleans better than products in which the aluminosilicate and alkali metal silicate have been spray-dried together.
These and other advantages to be obtained by the present invention are described hereinafter.
Throughout the specification and claims, percentages and ratios are by weight and temperatures are in degrees centigrade unless otherwise indicated.